Damping torsional vibrations in crank-shafts.



E'. W. LANCHESTER.

DAMPING TORSIONAL VIBRATIONS 1N CRANK SHAFTS.

APPLICATION FILED NOV, 28, 1910.

alu/U Patented Jan. 27, 19144.

INVEN R Frederick 'c1 unc ster BY f1 ATTORNEYS UNITED smilies; 'PATENTOFFICE.

.friannnnrcx WILLIAM LANCHESTER, or EDGBAsToN, BIRMINGHAM, ENGLAND.

Specification of Letters Patent.

Application filed November 28, 1910. Serial N o. 594,474.

' IJAMPING TORSIONAL AVIIBIRATION'S IN CRANKfSHAFTS.

Patented Jan.27, 1914.

To all whom it may concern.'

Be it known that I, FREDERICK WILLIAM LANoHEsTER, a subject of the Kingof Great Britain and Ireland, and residing at 53 Hagley road, Edgbaston,Birmingham, in the county of Warwick, England, have invented' certainnew and useful Improvements for Damping Torsional Vibrations inCrank-Shafts, of which the following is a specification.

erating through van elastic fluid, such elastlc means being adapted toabsorb excess ener during certain periods and to restore 'suc energy tothe system during certain suc- .ceeding periods'. VAgain, when a heavyflywheel has been employed for eliminating torque variations in.apparatus subjected to sudden stoppages, ithas been common, in order toprevent rupture of the shaft, to attach the flywheel to its shaft by adevice capable of slipping such as a friction clutch,

In high speed multicylinder internal combustion engines such as are usedin vehicle propulsion the elimination of torque variations is effectedin the usual way bv the use of a heavy iiywheel secured to e crankshaft. Such crank shafts present a new problem to the designer,however,- for at certain speeds of rotation it is found thatobjectionable,

such vibrations. K A crankshaft for multicylinder reciprocating engineswith several 'throws is a very elastic body, and is commonly loaded 'atone end or near one end by a flywheel of great moment of inertia, and isfurther loaded at different points along its length by inertia ableexciting torque.

and sometimes dangerous torsional vibrations are set up, and .object ofthe present invention'is to eliminate.

tain extent in the manner of a second flywheel, and this is especiallythe case in a six-throw crank. The crank shaft, therefore, isequivalent. to a torsionally elastic shaft with a distribution of bodieshaving moments of inertia along its length and it will be seen thatunder these conditions, torsional vibration may beset up by any suita Inmulticylinder reciprocating engines,

particularly internal combustion engines,

such torques exist im the intermittent impulses of the explosions, andin the inertia effects of the reciprocating masses. The piston andconnecting rod in reciprocation bring about a series of fouralternations of torque on the crank shaft during each revolution. If thevibration'-were strictly of the character which exists when a singlelength of shaft is fitted with two iiywheels rigidly attached, theresulting vibration would not be felt by the casing-of the en;

gine, because the whole of the torque variai tions in such a system areself-contained inV the rotating elements, and therefore, the

present invention does not apply to devices;

where parts in pure rotation are concerned.

Where, however, the second rotational partv exists partially or Whollyin the form. of reciprocating elements, the individual variations in theenergy of .these reciprocating4 elements result in considerable torquebeing set up, following the vibrations of the rotating system, butcommunicated to the stationary system of the engine. I have found thatthis form of vibration causes great.

trouble in the case of six-cylinder engines, as used in the automobileindustry, and results in the production of violent vibrations, which aretransmitted to the body ofthe car at and above certain definite speedsThe object of the invention is to dest-roy or diminish the synchronousvibrations above referred to, and so to render an engine of light weightand comparatively non-rigid construction,' free from vibration periodssuch as are commonly met with in engines at'present in use.

The invention consists in means for eliminating torsional vibration inthe crank shaft of a high speed reciprocating engine comprising arotational damper consisting of a body of adequate moment of inertiaconnected to the crank shaft by a yielding coupling o erating 'byfriction between surfaces or by uid,rictional or viscous action.

. cylinder motor with and the heavy Referring to the accompanyingdrawings, Figure 1 shows a crank shaft of a fourone form. of myinvention applied thereto; Fig. 2 shows a modified method of applyingthe invention; Fig. 3 shows a construction in which the coupling iseffected by means of fluid pressure.

In carrying the invention .into effect according to the modificationshown in Fig. 1 there is keyed to the rotating shaft a at the endfarthest from the flywheel b a coupling piece c provided with ribs dprojecting outwardly. Over the couplingpiece c there is fitted a heavywheel e .having internally projecting ribs f projecting between the ribsd of the coupling piece. rIhe heavy wheel e is provided with a bearing gon the crank shaft. A suitable oil film is formed between the heavywheel e and its ribs and the coupling piece c. In this form of theinvention if the shaft is rotating uniformly the heavy wheel e iscarried around at the same velocity as the shaft. If, however, owing to.the action of the connecting rods on the shaft, there 1s at any givenspeed a tendency to set up torsional oscillations at the end a of theshaft, these oscillations cause variations of speed between the end ofthe shaft aand the uniformly moving heavy wheel e, and the pull betweenthe coupling piece' c wheel e through the oil film will tend to damp outthese oscillations.

In the form of the invention shown in Fig. 2 the heavy wheel e is formedso that it takes a bearing on the Wheel h keyed to the-shaft a, an oillfilm being provided betweenthe wheels e and k.

In the form of the invention shownin Fig. 3 the heavy wheel e isprovided with a number of cylinders 0 in which work pistons connected byconnecting rods g with a sleeve r keyed to the shaft a. The spacebetween the pistons and the heads of the cyl- .inders is filled with asuitable liquid, and

suitable restricted passages a: arc provided whereby this liquid can beforced out or in should there be a tendency to relative movement betweenthe shaft and the heavy wheel. In this form 4of the invention it isessential that the wheel should do some work.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is 1. In a high speed reciprocating 'engine incombination a crankshaft having a number of cranks, a flywheel fixed onsaid crankshaft and means for preventing torsional vibration of saidshaft including a second flywheel mounted on said crankshaft at adistance from said fixed flywheel and a yielding coupling connectingsaid second flywheel to said crankshaft.

2. In a high speed reciprocating engine in combination a crankshafthaving a plurality of cranks, a flywheel fixed at one end of. saidcrankshaft andmeans for preventing torsional vibration of said shaftincluding a second flywheel applied to said crankshaft at a dista-ncefrom said first flywheel and a fluid frictional coupling connecting saidsecond flywheel to said crankshaft.

3. In a high speed reciprocating engine in combination a crankshafthaving a plurality of cranks, a flywheel fixed at one end of saidcrankshaft and vmeans for preventing torsional vibration of said shaftincluding a member attached to said crankshaft at a distance from saidflywheel said member h aving a projecting surface, a heavy wheel havingAal surface opposed to said projecting surface and an oil film betweensaid surfaces, as set forth.

4. In a high speed reciprocating engine in combination -a crankshafthaving a plurality of cranks, a flywheel fixed at one end of saidcrankshaft and means for preventing torsional vibration of said shaftincluding a member keyed to the other end of said crankshaft, a numberof disks attached to said member and projecting in a radial direction, asecond flywheel, a number of rings projecting from said flywheelbetween'said disks, and oil films between said rings and disks, as setforth. f

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

FREDERICK wlmin LANcnEsrER.

Witnesses JOBN MORGAN, HARRY Davis.

